Wide hybridization for crop improvement GPB

Wide Hybridization for Crop Improvement GPB

1. Department of Genetics and Plant Breeding Brahma Nand Mahavidyalaya Rath Hamirpur UP. COURSE SEMINAR ON Wide Hybridization for Crop Improvement Under the guidance of Presented by

2. Introduction History Features of distant hybridization Problems associated with wide cross Techniques to make wide crosses successful Limitations of Distant hybridization Content

3. INTRODUCTION Hybridization Crossing between two genetically dissimilar parent is called hybridization. Distant Hybridization Hybridization between individuals from different species, belonging to the same genus or to different genera is termed as distant hybridization and such crosses are known as distant crosses or wide crosses. ( i ) Intergeneric Hybridization When the individuals being crossed belong to species from two different genera it is referred as intergeneric hybridization. e.g. Triticum spp. X rye ( Secale cereale ). (ii) Interspecific Hybridization When the individuals from two distinct species of the genus are crossed, it is known as inter specific hybridization. e.g. Oryza sativa x Oryza perennis .

4. History Thomas Fairchild (1717): First authentic record of a distant hybridization for crop improvement is the production of a hybrid between Carnation ( Dianthus caryophyllus ) and Sweet William ( Dianthus barbatus ). Rimpu (1890): Produce the first intergeneric hybrid triticale which have greater potential than Raphanobrassica . Karpechenko (1928): An interesting intergeneric hybrid, Raphanobrassica , ( R. sativus x B. oleracea ) was produced. Thomas Fairchild Karpechenko

5. Objectives of Distant Hybridization Wide crossing or distant hybridization has been used in the genetic improvement of some crop plants. It is an effective means of transferring desirable genes into cultivated plants from related species and genera those are not available in cultivated varieties. ( i ) Many disease resistance and, insect resistance genes (ii) Wide adaptability: ( i.e. drought-resistance, cold tolerance etc.) (iii) Quality improvement ( Eg. fibre quality in Cotton) (iv) Yield improvement ( Eg. Oats, Tobacco, Maize, Sugarcane) (v) Other characters ( Eg. CMS, Earliness, dwarfness, morphological characters) (vi) Exploitation of luxuriance (heterosis) in vegetatively propagated/ornamental crops. (vii) Prolonged vegetative period, Prolonged blooming period (viii) Creation of Novel genotypes: New species or F1 hybrids not existing in nature.

6. 1. It is used when the desirable character is not found within the species of a crop.   2. It is an effective method of transferring desirable gene into cultivated plants from their related cultivated or wild species.   3. It is more successful in vegetatively propagated species like sugarcane and potato than in seed propagated species.   4. It gives rise to three types of crosses viz. a) fully fertile, b) Partially fertile and c) Fully sterile in different crop species.   5. It leads to introgression which refer to transfer of some genes from one species into genome of another species.   6. F1 hybrid between two genus are always sterile. The fertility has to be restored by doubling of chromosome through colchicine treatment . Main features of Distant Hybridization

7. The major problems associated with wide crosses are: Cross Incompatibility Hybrid In viability Hybrid Sterility Hybrid Breakdown CROSS INCOMPATIBILITY This is the inability of the functional pollen grains of one species or genus to effect fertilization in another species or genus. There are three main reasons of cross incompatibility viz. Lack of pollen germination. Insufficient growth of pollen tube to reach ovule. Inability of male gamete to unite with the egg cell. Problems associated with wide crosses

8. 2. HYBRID INVIABILITY This refers to the inviability of the hybrid zygote or embryo. In some cases, zygote formation occurs, but further development of the zygote is arrested. In some other cases, after the completion of the initial stages of development, the embryo gets aborted. The reasons for this are: Unfavorable interactions between the chromosomes of the two species Unfavorable interaction of the endosperm with the embryo. Disharmony between cytoplasm and nuclear genes 3. HYBRID BREAKDOWN Hybrid breakdown is a major problem in interspecific crosses. When F 1 hybrid plants of an interspecific crosses are vigorous and fertile but there F 2 progeny is weak and sterile it is known as hybrid breakdown. Hybrid breakdown hinders the progress of interspecific gene transfer. This may be due to the structural difference of chromosomes or problems in gene combinations.

9. 4. HYBRID STERILITY This refers to the inability of a hybrid to produce viable offspring. This is more prominent in the case of intergeneric crosses. The major reason for hybrid sterility is the lack of structural homology between the chromosomes of the two species. This may lead to meiotic abnormalities like chromosome scattering, chromosome extension, lagging of chromosome in the anaphase, formation of anaphase bridge, development of chromosome rings and chains, and irregular and unequal anaphase separations. These irregularities may lead to aberrations in chromosome structure. Lack of homology between chromosomes may also lead to incomplete pairing of chromosomes.

10. SELECTION OF PLANTS The most compatible parents available should be selected for the crosses. RECIPROCAL CROSSES Reciprocal cross may be attempted when one parental combination fails. e.g. Mung x urd -cross compatible and Urd x mung -cross incompatible. MANIPULATION OF PLOIDY Diploidization of solitary genomes to make them paired will be helpful to make the cross fertile. TECHNIQUES TO MAKE WIDE CROSSES SUCCESSFUL

11. BRIDGE CROSSESS When two parents are incompatible, a third parent that is compatible with both the parents can be used for bridge crosses and thus it becomes possible to perform cross between the original parents. e.g. Tobacco Nicotiana repanda x N. tabaccum - cross incompatible Nicotiana repanda x N. sylvestris - cross compatible N icotiana sylvestris x N. tabaccum - cross compatible USE OF POLLEN MIXTURE Unfavorable interaction between pollen and pistil in the case of wide crosses can be overcome to some extent by using pollen mixture.

12. MANIPULATION OF PISTIL Decapitation of the style will sometimes prove helpful in overcoming incompatibility. USE OF GROWTH REGULATORS Pollen tube growth can be accelerated by using growth hormones like IAA, NAA, 2,4-D and Gibberellic acid. PROTOPLAST FUSION When fusion of gametes fails, protoplast fusion of somatic cells can be attempted. EMBRYO RESCUE Hybrid zygotes formed by wide crosses may fail to grow in a number of cases. The zygotes are taken out and grown in in vitro medium to overcome this problem.

13. Incompatible crosses F1 sterility Problems in creating new species Lack of homoeology between chromosome of the parental species Undesirable linkages Problems in the transfer of recessive oligogenes and quantitative traits Lack of flowering in F1 Problems in using improved varieties in distant hybridization. Limitations of Distant hybridization

14. CASE STUDY

15. Production of Interspecific hybrids between Gossypium hirsutum and Jassid Resistant wild species G. raimondii and G. armourianum

16. Material used 12 Gossypium hirsutum genotypes (tetraploid) and 2 Jassid resistant wild (diploid) species viz., Gossypium raimondii and G. armourianum . The selfed seeds of G. hirsutum genotypes were obtained from the germplasm collections maintained at the Cotton Breeding Station, TNAU, Coimbatore, Tamil Nadu, India. In order to incorporate the jassid resistance, the crosses were effected between cultivated tetraploids and wild diploids and 24 crosses were made.

17. RESULT

18. In the present study, in diploid and tetraploid species, normal orientation, association and disjunction of chromosomes occurred in tetraploids and diploids while in triploids, trivalents with low frequency of chromosome associations were observed. The formation of trivalents and higher chromosome associations indicate the pairing affinities between the genomes involved. Cytological analysis of the hybrids revealed that they were true interspecific crosses. Observations of meiotic metaphase chromosomes indicated the degree of relatedness between species. As expected, chromosome pairing indicated a close homology of G. armourianum (D2-1) and G. raimondii (D5) with D sub-genome of the G. hirsutum . It is discernible from the present study that the greater homology observed between A and D genomes aid in production of desirable recombinants despite minor cytological disturbances as there are successful boll setting and viable seed production. Hence, these species with D genome can be used successfully in transferring jassid resistant genes to cultivated cotton as host plant resistant source as an ecofriendly and viable source of resistance. CONCLUSION

19. REFERENCES Groot, M. H., van de Wiel , C. C., van Tienderen , P. H. & den Nijs , H. C. (2003). Hybridisation and introgression between crops and wild relatives.  Current knowledge and research priorities in lieu of impending introductions of GM crops: COGEM research report. University of Amsterdam & Plant Research International, Amsterdam & Wageningen . Mudhalvan , S., Ramesh, P. K., Lakshmi, B., Vamsi, B. K., Ajmal, H., Pandiyaraj , P. & Jeyaprabha , J. (2024). A Review on Role of Wide Hybridization in Crop Improvement.  International Journal of Plant & Soil Science ,  36 (6), 652-658. Pushpam , R. & Raveendran, T. S. (2006). Production of interspecific hybrids between Gossypium hirsutum and Jassid resistant wild species G . raimondii and G. armourianum .  Cytologia ,  71 (4), 407-418.

20. Richard, A. J. (2005). Hybridisation ‐Reproductive Barriers to Gene Flow.  Gene flow from GM plants , 78-112. Wong, E. L., Hiscock, S. J. & Filatov , D. A. (2022). The role of interspecific hybridisation in adaptation and speciation: Insights from studies in Senecio.  Frontiers in Plant Science ,  13 , 907363.

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